**5. Conclusions**

*Urban Horticulture - Necessity of the Future*

other viruses. The influence of peppermint essential oil (P-EO) on the surface of hydroxyapatite nanoparticles was studied [90] related to their morphological, physicochemical and antimicrobial properties. The results of the qualitative antimi-

Antimicrobial qualitative assay revealed that the peppermint had a significant inhibition effect on the microbial growth of the tested microorganisms, with the inhibition diameter ranging from 6 to 22 mm. The solvent DMSO did not affect the growth on solid media of any tested microbial strains. HAp had no inhibitory effect on the growth of the tested microorganisms and the most pronounced inhibition was observed in the case of *E. coli* tested strains in its two forms. The diameter of the inhibition growth area was 22 mm to 20 mm in the case of P-EO and a smaller inhibition zone of 8 mm for HAp-P. On *S. aureus* the inhibitory effect was related notably for P-EO and HAp-P with an inhibition zone in the range 7–8 mm. Essential oil extracted from peppermint contains active constituents that are responsible for eliminating bacterial pathogens, i.e. P-EO and HAp-P presented significant antibacterial activity with constituents acting on the cell membrane causing important morphological damage and destabilization of microbial membrane. Due to the worldwide emergence of *S. aureus* and *E. coli* strains which are resistant to conventional antibiotic therapy, there have been major concerns in public health area that conduced to the necessity of the developing of new antimicrobial compounds. Nano-sized powders of HAp doped with several metal ions that are known to possess antimicrobial properties as silver, zinc or cerium are used together with HAp in combination with essential oils. The effect of plants EOs and plants EOs-HAp combination regarding the antimicrobial activity is presented [91] in **Table 2** related to the diameter of inhibition zone-inhibition growth of tested

The lavender EO inhibited the growth of all tested bacterial strains, as indicated the formation of inhibition zone ranged from 16 mm (*E. coli* ESBL 4493) to 24 mm (MRSA 1144). The HAp-L material was active against tested bacterial strains compared to HAp. The basil EO and HAp-B samples exhibited a lower inhibitory effect against the tested bacteria. On the other hand, HAp material had no effect on

The possibility of covering hydroxyapatite with different molecules, e.g. essential oils offer a solution to apply in food industry, in the idea that HAp is an essential component of human organism. In this regard, the potential use in medicine e.g. bone reconstruction could help the reducing of postoperative infections after different implants. In the case of hydroxyapatite nanotechnology have opened the gate to different applications in agriculture, food industry, medicine with the final target of improving human health and resistance to a continuous modification of

crobial properties of P-EO and HAp-P are presented in **Table 1**.

**66**

**Table 1.**

bacterial strains.

pathogen agents.

the growth of the selected bacteria.

*The diameters of inhibition growth zones (mm).*

As it was presented, in the last few decades, nanotechnology reveals its benefit usage in different activity fields and in particular in biotechnology and agriculture. Fertilizer compounds are essential for our quality of soil and water for the development of plants in order to increase the crops in order to cover what is needed to sustain the food necessities all over the world. Therefore there exist a necessity to decrease nutrient casualties in fertilization, and to amplify the plant product by the operation of novel uses with assistance of nanotechnology and nanomaterials. This type of fertilization delivers the nutrients on request, control the use of chemical fertilizers that regulate growth and development of plants and raise the activity of target vegetal organism. In this regard have been presented the effects of different nanomaterials and nanoparticles upon selected plants culture as wheat, maize, soybean, etc. taking into account their growth morphological parameters and the nanoparticles influence upon plant metabolism. The present and future use of nanoparticles as micronutrients is affected by different risks related to nanotoxicity of micronutrients, a problem to be solved by an appropriate and safe circuit of nanoparticles in soil, water, plants and at last in human organism. In this regard, it is important to quantify nanomaterials concentration in water, soil and air, where the concentration of relevant nanomaterials is essential to define exposure, a problem to be solved by the modeling of environmental concentrations. Due to the rapid development of manufactured nanomaterials it is important to evaluate their environmental and health impact, and it was stated to assure a safe circuit from micronutrients used for plants crop increasing to the beneficiaries of these plants, i.e. animals and humans. The present work is an approximately extensive presentation of the present status of the application of nanomaterials and nanoparticles in agriculture i.e. in plants fertilization with accent to the plants growth parameters, possible toxic risks and application to the antimicrobial activity.
